What Do Moths Eat?

Keratin is Key

Proteins are the building blocks of life. For an insect to survive, it must eat a diet containing protein. Humans get their protein from a variety of sources, including meat, fish, eggs, milk, seeds, nuts, fruits, and vegetables. What about moths?

Moths eat a very simple diet. So simple, in fact, that it consists of only one type of proteinkeratin 

Keratin is the key structural protein making up hair, nails, feathers, horns, claws, hooves, and fur among vertebrates. 

The reason clothes moths are so resilient rests on the simplicity of their diet. Anywhere keratin byproducts can be found, clothes moths can survive. Clothes moths are unique because few species in the animal kingdom are able to digest keratin.

Moths can cause significant damage to keratin-containing fabrics made of natural fibers, like silk and wool. The name “clothes moth” is a misnomer, because these insects also eat carpet, tablecloths, and handmade rugs.

 

cocoon

"Are You Sure? I See Holes in My Viscose Sweater!"

This is where things get complicated. While I have personally observed moths devour articles of clothing that do not contain keratin—such as viscose, cotton, rayon, and polyester—from a nutritional perspective, it should not be possible for these creatures to ingest only manmade fibers and receive the nourishment needed to weave their cocoons and reproduce. Your eyes are not deceiving you.

Take A Look at This!

I would like to proffer the following piece of direct evidence for the consumption of artificial fibers by clothes moths. Here’s an example of an acrylic sweater that somehow provided enough sustenance to allow this moth to eat a grand buffet dinner every day, weave his cocoon, and fly away!

Acrylic fibers are synthetic fibers made from vinyl acetate or methyl acrylate with an average molecular weight of ~100,000, about 1900 monomer units. For a fiber to be called “acrylic” in the US, the polymer must contain at least 85% acrylonitrile monomer.

So… moths eat plastic?

moth cocoon
Exhibit A: 100% acrylic sweater
moth cocoon
Exhibit B: moth doesn't care!

The Moth Guy's
Theory of Mysterious Sweater Holes

moth guy
When I'm not observing moths, I'm in my office writing about them so you don't have to.

From observing moths for over five years, I have had no choice but to come to the troubling conclusion that even your synthetic fibers are not safe from moths. In numerous situations, I have observed these creatures devour fabrics that on their face appear to have no nutritional value whatsoever. How is this possible?

When I was observing the moths consume artificial fibers, I did notice something interesting. I did not observe any environment where all three of the below criteria were satisfied and the moths still ate the synthetic fibers:

  1. Pets were present, including cats. Cats emit large quantities of proteins through their saliva which diffuses into the environment through their fur and dander.
  2. Synthetic fibers were adjacent to natural fibers. Some articles in the closet were made of wool or silk.
  3. The closet was dusty. Dust is comprised mostly of dead skin cells, which contain keratin.

Therefore, I believe that in situations where you are observing artificial fibers being eaten by moths, it is highly likely that they are consuming keratin that is diffused in the environment, whether it is engrained in the fibers, on surfaces, or in the air. This allows the moths to eat and weave plastic fibers that are coated with a delicious, razor-thin layer of keratin.

So there you have it, folks. You heard it here first.

To Summarize

  1. Moths need keratin to survive.
  2. Although your synthetic fibers may not contain keratin on the inside, there may be microscopic amounts of keratin on the outside that moths can eat.
  3. Keratin can get on clothes from pets, dust, or other natural fibers.
  4. Regularly wash your synthetic clothes to remove keratin and prevent them from being eaten.

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